Simulation analysis method for tackifying reaction process of polyester falling film

Abstract

The invention relates to the field of chemical engineering, and discloses a polyester falling film tackifying reaction process simulation analysis method. According to the method, a polyester falling film tackifying reaction process model is established by adopting a numerical calculation and process simulation software interaction method, and a polyester falling film tackifying process material balance equation is subjected to decoupling calculation by utilizing physical equations such as reaction kinetics, mass transfer kinetics and hydrodynamics; basic physical quantity distribution (such as intrinsic viscosity, molecular weight, terminal carboxyl group content and the like) of a polyester falling film reaction process can be effectively and conveniently obtained, so that a good guiding effect is provided for experimental research and industrial design. Meanwhile, the falling film tackifying reaction process simulation analysis method provided by the invention has certain universality and can be applied to simulation of various polyester falling film melt polycondensation reactions.

Description

Technical Field

[0001] The invention relates to the field of chemical industry, and in particular to a simulation analysis method for a polyester falling film viscosity increasing reaction process. Background Art

[0002] Polyester is one of the most important polymers today, including aliphatic polyesters such as polybutylene succinate (PBS), semi-aromatic polyesters such as polyethylene terephthalate (PET), fully aromatic polyesters such as parabens (PHB), modified copolyesters such as poly(butylene terephthalate-butylene adipate) (PBAT), carbonate-based polyesters such as bisphenol A polycarbonate (PC), etc. Various types of clothing, curtains, films, drinking bottles, household appliance housings, car lampshades, switches and sockets used in daily life, as well as industrial products such as car seat belts, industrial products tire cords, advertising cloths, mooring ropes, etc. are all polyester products. In the process of industrial production of polyester, a melt polycondensation reaction is usually required after esterification. When the mechanical properties of the product are required to be higher, a further polycondensation step is generally required to further increase the molecular weight.

[0003] The melt polycondensation reaction process and technology are the core links of polyester production. The chain growth reaction process of further converting short-chain polyester molecules into high molecular weight polyester under the reactor structure and process conditions of the set structure directly affects the production efficiency and product quality of polyester. When it is necessary to improve the efficiency of the melt polycondensation reaction, the existing conventional melt polycondensation reaction is limited by the melt flow structure and cannot achieve the improvement of the melt polycondensation reaction efficiency, or when it is necessary to further quickly increase the molecular weight of polyester, it is forced to adopt a long process and high energy consumption solid phase polycondensation route.

[0004] Falling film flow has excellent characteristics such as large film-forming area and high gas-liquid heat and mass transfer efficiency, but its flow structure is large in scale and it is time-consuming and labor-intensive to carry out the gas-liquid flow process under actual working conditions. Moreover, when the fluid object is a highly viscous polymer melt undergoing a harsh melt polycondensation reaction, the construction and operation costs of the experimental device are too high, and it is impossible to conduct process analysis and efficiently obtain a large amount of experimental result data. Through process simulation, the falling film melt polycondensation reaction process and result analysis can be effectively carried out to explore the falling film viscosity reaction effect.

[0005] Through the search of the prior art, it is found that there is no report on the process simulation of polyester falling film melt polycondensation reaction process and result analysis to explore the effect of falling film viscosity reaction. Therefore, there is an urgent need for methods and technologies that can effectively and conveniently analyze the material flow process under the actual working conditions of polyester falling film viscosity enhancement and the distribution of basic physical quantities (such as viscosity, terminal carboxyl and terminal vinyl content, etc.) at various axial positions in the reaction, so as to understand the reaction law of the continuous polymerization-viscosity enhancement production process and provide effective guidance for experimental research and industrial design. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a simulation and analysis method for the falling film viscosity-increasing reaction process of polyester. The present invention adopts the method of interaction between numerical calculation and process simulation software to establish a polyester falling film viscosity-increasing reaction process model, and uses physical equations such as reaction kinetics, mass transfer kinetics and fluid dynamics to decouple the material balance equation of the polyester falling film viscosity-increasing process, so as to effectively and conveniently obtain the basic physical quantity distribution (such as characteristic viscosity, molecular weight, terminal carboxyl content, etc.) of the polyester falling film reaction process, thereby providing a good guide for experimental research and industrial design. At the same time, the simulation and analysis method for the falling film viscosity-increasing reaction process proposed by the present invention has certain versatility and can be applied to the simulation of various polyester falling film melt polycondensation reaction processes.

[0007] The specific technical solution of the present invention is: a simulation analysis method for a polyester falling film viscosity increasing reaction process, which comprises:

[0008] Conduct polymerization reaction kinetic model analysis, gas-liquid two-phase mass transfer analysis, and falling film fluid dynamics analysis on polyester;

[0009] The reaction kinetics model, gas-liquid two-phase mass transfer model and fluid dynamics model were used to perform material balance on the entire polyester falling film viscosity increasing reaction process, boundary conditions and initial conditions were set, and the material balance equation was solved by numerical calculation to establish the polyester falling film viscosity increasing reactor model.

[0010] The entire process of polyester melt falling film viscosity increasing reaction is constructed according to the polyester reaction production process. The index parameters of polyester melt with a certain degree of polymerization obtained by polycondensation are used as input values, and the partial differential equations of the reaction rate are calculated. The performance parameters of the polymerization product and the content information of each characteristic component are output, and the simulation results of the polyester falling film viscosity increasing reaction process are analyzed.

[0011] The falling film viscosity increasing reactor is usually equipped with a melt cavity, a film structure, and a falling film support that can support the flow of the melt fluid. The polyester melt that has undergone polycondensation flows along the axial direction of the falling film support while completing the volatilization and viscosity increasing reaction of the small molecule by-products of the polycondensation, thereby achieving an increase in molecular weight.

[0012] The method of the present invention is applicable to the prepolymerization reaction after esterification, the polycondensation reaction after the prepolymerization reaction, and the secondary and higher polycondensation reactions. The principle of the present invention is based on the high viscosity characteristics of the polyester material melt, which maintains the characteristics of plug flow motion during the wall-attached falling film flow, can always maintain a large film-forming area, and effectively improve the gas-liquid interface renewal rate. On the basis of fully understanding the mass transfer characteristics of the polycondensation reaction and the fluid dynamics of high-viscosity materials, the falling film flow is used to strengthen the polymer devolatilization, and the application results of this technology are obtained by process simulation.

[0013] Preferably, the polymerization reaction kinetic model includes the chain growth reaction process of generating by-products of water and hydroxyl compounds; more preferably, it also includes but is not limited to the production of by-products of terminal olefin compounds, aldehydes, hydroxyl condensates, ...

[0014] The polymerization reaction kinetics model analysis comprises the following steps:

[0015] (1) Determine the main reaction and side reactions in the polymerization process: Use the "chain segment analysis" method to simplify the reaction into a limited number of basic chain segment units, with the condensation chain growth reaction as the dominant reaction, and determine the reaction equations for the generation of aldehydes, hydroxyl compounds, hydroxyl condensates, water, and terminal olefin groups;

[0016] (2) Determination of reaction rate constant and equilibrium constant: Describe the effect of temperature on the reaction rate constant using the Arrhenius equation, specify the pre-exponential factor and activation energy in the equation, determine the reversible reaction equilibrium constant, and solve for the forward and reverse reaction rate values;

[0017] (3) Establishing reaction kinetic equations: Use the reaction kinetic model to analyze the reaction kinetic equations of each component, and compile and import the established equation group into an executable function script file in the numerical calculation software.

[0018] Preferably, the gas-liquid two-phase mass transfer analysis comprises the following steps:

[0019] (1) According to the component targets to be analyzed in the gas-liquid two-phase, select an appropriate physical property model and set relevant property values, including but not limited to one or more of relative molecular mass, critical temperature, pressure, compressibility, gas-liquid phase pressure, molar volume, polymer molecular weight and viscosity characteristic parameters, and store the properties in a global data array;

[0020] (2) A simulation analysis method for the devolatilization process of small molecules in high-viscosity polymer melts. According to the gas-liquid phase equilibrium process, the volatile components in the system are determined, the gas-liquid equilibrium equation at the interface is constructed by calling the attribute groups of each component, and the corresponding settings are made in the numerical calculation software;

[0021] The volatile components are specifically: according to the significant influence of each volatile component on the reaction process, the volatile components in the gas phase include but are not limited to hydroxyl compounds and water, and the volatile components in the liquid phase include but are not limited to hydroxyl compounds, water, condensates of hydroxyl compounds and aldehydes, and the phase equilibrium process parameters are set for the volatile components in the gas and liquid phases;

[0022] (3) Determine the reactor equipment structure and process condition parameters of the falling film viscosity increasing reaction process that affect the gas-liquid mass transfer rate, introduce the mass transfer coefficient to calculate the mass transfer flux of the gas phase components, and iteratively calculate the mass transfer coefficient based on the gas phase mass transfer flux during the operation of the reactor in industry;

[0023] (4) Initialize the output attribute group of each component to complete the iterative solution calculation and obtain the mass transfer flux of the gas phase volatile component in the polyester falling film viscosity increasing reaction process.

[0024] Preferably, the falling film fluid dynamic behavior analysis includes the following steps: determining the molecular diffusion coefficient in the flow process according to the low-speed laminar polymer motion under extremely low Reynolds number, establishing the convection-diffusion equation, and setting relevant model parameters in the numerical calculation software, including material flow rate, dynamic viscosity and flow velocity of micro-elements in the free falling liquid film area.

[0025] Preferably, the construction of the polyester falling film viscosity increasing reactor model comprises the following steps:

[0026] (1) Based on the polymerization reaction kinetics, gas-liquid mass transfer kinetics and falling film fluid dynamics, the volume microelement mass balance equation along the axial flow direction of the fluid in the falling film viscosity increasing reactor was established;

[0027] (2) Boundary conditions were set according to the operating parameters of the falling film viscosity increasing reactor in industry, the discrete format was selected, and the material balance equation was solved using the numerical integration method;

[0028] (3) Define and initialize variables, constants, and parameters, use the software solver to solve the material balance equation, and output key process performance indicators for the gas and liquid phases.

[0029] Preferably, in the step (3) of constructing the polyester falling film viscosity increasing reactor model, the variables, constants and parameters include one or more of the number of components, the number of discrete points in the spatial direction, the number of ordinary differential equations to be solved, and the flow rate of the molten polymer; the key process performance indicators of the gas-liquid phase include one or more of the number average molecular weight, the intrinsic viscosity and the terminal carboxyl content.

[0030] Preferably, the construction of the whole process of the polyester melt falling film viscosity increasing reaction includes the following steps:

[0031] (1) calling the automatic control interface of the process simulation software to import the discharge data output from the previous reaction process of the falling film viscosity increasing reactor as the model input value, running the numerical calculation software to calculate the material balance equation, and obtaining the change of variables with the reaction progress;

[0032] (2) Create a component object model object for process simulation, open and run the model file, set the user interface visibility, and run it in the numerical calculation software to obtain the output information of each component.

[0033] Preferably, in step (1) of constructing the entire process of the polyester melt falling film viscosity increasing reaction, the automatic control interface (ActiveX) of Aspen Plus is called to import the discharge data output by its process as the model input value, and MATLAB is run to calculate the material balance equation to obtain the change of variables with the reaction progress.

[0034] Further preferably, the ActiveX interface specifically includes: creating a component object model object of Aspen Plus, opening and running the model file according to the .bkp file path, setting the user interface visibility, and running in MATLAB to obtain and output information of each component.

[0035] Further preferably, the variables include but are not limited to one or more of the molecular weight of the polymer product, the concentration of terminal carboxyl groups, the concentration of terminal hydroxyl groups, the content of hydroxyl condensates, and the intrinsic viscosity.

[0036] Preferably, the analysis of the simulation results of the polyester falling film viscosity increasing reaction also includes carrying out process simulation calculations of different falling film viscosity increasing reactor operating conditions, and analyzing the influence of the operating conditions on the falling film viscosity increasing reaction effect.

[0037] The specific steps of analyzing the simulation results of the falling film viscosity increasing reaction of polyester include: importing the process simulation file into the numerical calculation software for processing, outputting and displaying the acquired data as one or more of a data table, a graph or a curve, observing and analyzing the results of the simulation calculation, and understanding the distribution of the performance indexes of each axial component in the falling film viscosity increasing process;

[0038] Further preferably, the specific steps of analyzing the simulation results of the falling film viscosity increasing reaction of the polyester include: importing the Aspenplus simulation file into the MATLAB software for processing, outputting and displaying the acquired data as a graph or curve, observing and analyzing the results of the simulation calculation, and understanding the distribution of the performance indicators of each axial component in the falling film viscosity increasing process;

[0039] The specific steps for analyzing the operating conditions of the falling film viscosity increasing reaction simulation of polyester include: in the numerical calculation software, iterative cycle calculation of the falling film viscosity increasing reactor unit module is performed, and the influence of different operating parameters on the reaction effect is systematically adjusted and analyzed. Through multiple simulation runs, key data of the operation is collected and compared and analyzed.

[0040] Further preferably, the specific steps of analyzing the operating conditions of the simulated polyester falling film viscosity increasing reaction include:

[0041] In MATLAB software, the falling film viscosity increasing reactor unit module is iteratively calculated, and the influence of different operating parameters (such as temperature and pressure) on the reaction effect is systematically adjusted and analyzed. Through multiple simulation runs, key operation data (such as reaction product concentration, polymer molecular weight, viscosity change, etc.) are collected and compared and analyzed.

[0042] Further preferably, the different operating parameters include one or more of temperature and pressure; and the key data include one or more of reaction product concentration, polymer molecular weight and viscosity change.

[0043] Preferably, the polyester includes aliphatic polyesters, semi-aromatic polyesters and aromatic polyesters, copolyesters and modified products with polyester content of not less than 80% containing ester groups or carbonate groups on the main chain; further preferably, the polyester refers to semi-aromatic polyesters, copolyesters and modified products thereof with ester content of more than 85% on the main chain of the molecule obtained by reacting divalent or higher carboxyl and hydroxyl monomers, or esters thereof with the monomers;

[0044] More preferably, the polyester refers to bisphenol A polycarbonate containing carbonate groups;

[0045] More preferably, the polyester is a polyester obtained by reacting a semi-aromatic dicarboxylic acid and an aliphatic diol.

[0046] Compared with the prior art, the beneficial effects of the present invention are:

[0047] (1) The present invention can intuitively provide the axial distribution of key component performance indicators during the falling film viscosity increasing process of polyester in a falling film viscosity increasing reactor and the axial distribution of key component performance indicators under the influence of different temperatures and pressures; it can directly feedback the distribution law of various indicators of the polyester melt during the falling film viscosity increasing reaction process, thereby judging the quality of the export product under the current working conditions.

[0048] (2) The present invention can simulate and calculate the flow and reaction process in the falling film viscosity increasing reactor during the falling film viscosity increasing reaction of the polyester, and can effectively and conveniently obtain the axial distribution of the performance indicators of the key components at various positions in the falling film viscosity increasing reactor (such as molecular weight, viscosity, terminal carboxyl content, etc.), thereby providing a good guide for experimental research and industrial design. At the same time, the polyester falling film viscosity increasing reaction process simulation method proposed in the present invention has a certain degree of versatility.

[0049] (3) The present invention is applicable to the simulation of the distribution of performance indicators of components outside the melt tube during the falling film viscosity increasing process of polyester in the falling film viscosity increasing reactor and the process operation condition analysis method, which provides a theoretical basis for industrial operation, promotes the melt polycondensation of various polyesters to increase the molecular weight, and realizes the design and development of high molecular weight polyester melt direct spinning process, provides a comprehensive and reliable modeling method for the development of melt polycondensation reactors, saves development costs, and has good application prospects and economic value.

[0050] (4) The present invention uses the interactive method of MATLAB and Aspen Plus to establish a falling film viscosity-increasing reaction process model, which fully considers the physical and chemical changes within the reaction, overcomes the shortcomings of large experimental test investment and long cycle, and can predict the distribution of performance indicators of key components in the reaction process, thereby realizing the analysis of the falling film melt polycondensation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the free falling liquid film flow attached to the wall on the internal components of the falling film viscosity increasing reactor;

[0052] Figure 2 It is MATLAB workflow diagram of the present invention;

[0053] Figure 3 It is the process flow model diagram of Aspen Plus software of the present invention;

[0054] Figure 4 It is a workflow diagram of the interaction between MATALB and Aspen Plus of the present invention;

[0055] Figure 5 This is the molecular weight axial distribution diagram during the falling film viscosity increasing reaction of the present invention;

[0056] Figure 6 The axial distribution diagram of the terminal carboxyl group and the terminal hydroxyl group during the falling film viscosity increasing reaction of the present invention;

[0057] Figure 7 The axial distribution diagram of diethylene glycol and terminal diethylene glycol groups during the falling film viscosity increasing reaction of the present invention;

[0058] Figure 8 The molecular weight axial distribution diagram of the film viscosity enhancement reaction process at different temperatures of the present invention;

[0059] Fig. 9 The axial distribution diagram of the terminal carboxyl group during the film viscosity enhancement reaction at different temperatures of the present invention;

[0060] Fig.10 The axial distribution diagram of the end vinyl group during the film viscosity enhancement reaction at different temperatures of the present invention;

[0061] Fig.11The molecular weight axial distribution diagram during the film viscosity enhancement reaction under different pressure drops of the present invention;

[0062] Fig.12 This is the axial distribution diagram of the terminal carboxyl group during the film viscosity enhancement reaction under different pressure drops of the present invention. DETAILED DESCRIPTION

[0063] In order to further understand the embodiments of the present invention, the present invention is further described in detail below in conjunction with specific implementation methods, and the content does not affect the scope of protection of the present invention.

[0064] Example 1

[0065] The present invention uses MATLAB and Aspen Plus software to interact to simulate the falling film viscosity increasing reaction process of polyester (PET), including the construction of a falling film viscosity increasing reactor unit module that couples reaction kinetics, gas-liquid two-phase mass transfer kinetics and falling film fluid dynamics in MATLAB, the construction of the whole falling film viscosity increasing process after running Aspen Plus, and the analysis of simulation results and process operating conditions after running MATLAB. Specifically:

[0066] (I) Analysis of the polymerization reaction kinetics model of polyester

[0067] First, determine the main and side reactions of the polymerization process: use the "chain segment analysis" method to simplify the reaction into a combination of a finite number of basic chain segment units, with the polycondensation chain growth reaction as the main reaction, and determine the side reaction equations for the generation of acetaldehyde, diethylene glycol, water, and terminal vinyl groups. Use the Arrhenius equation to describe the effect of temperature on the reaction rate constant, specify the pre-exponential factor and activation energy in the equation, determine the reversible reaction equilibrium constant, and solve the forward and reverse reaction rate values. Use the secondary reaction kinetics model to analyze the reaction kinetics equations of each component, and compile the established equation group into the executable function script file of MATLAB. Taking the main reaction of polyester polycondensation chain growth as an example, use the secondary reaction kinetics to determine the reaction rate equation, and use the Arrhenius equation and empirical data to calculate its reaction equilibrium constant. Use a custom program to compile the rate equation into an executable script for calculation.

[0068] (II) Gas-liquid two-phase mass transfer analysis of polyester

[0069] According to the component targets that need to be analyzed in the gas-liquid two phases, select the appropriate physical property model and set the relevant property values, including relative molecular mass, critical temperature, pressure, compressibility, gas-liquid phase pressure and molar volume, polymer molecular weight and viscosity characteristic parameters, and store the properties in the global data array; for the simulation analysis method of the small molecule devolatilization process of high-viscosity polymer melt, according to the gas-liquid phase equilibrium process, simplify the volatile components in the system, call the property groups of each component to construct the gas-liquid equilibrium equation at the interface, and make corresponding settings in MATLAB.

[0070] The volatile components are specifically: according to the significant influence of each volatile component on the reaction process, the volatile components in the gas phase mainly include ethylene glycol and water, and the liquid phase contains ethylene glycol, water, diethylene glycol and acetaldehyde. Phase equilibrium process parameters are set for the volatile components in the gas and liquid phases.

[0071] The gas-liquid equilibrium equation at the interface is determined as: the components involved are ethylene glycol, water and diethylene glycol; the saturated vapor pressure and molar volume of the components involved are calculated.

[0072] (III) Analysis of the falling film hydrodynamic behavior of polyester

[0073] The influence of the reactor equipment structure and process conditions (temperature, pressure) on the gas-liquid mass transfer rate in the falling film viscosity increasing reaction process is determined, and the mass transfer coefficient is introduced to calculate the mass transfer flux of the gas phase components. The mass transfer coefficient is iteratively calculated based on the gas phase mass transfer flux when the reactor is running in industry, and the output property group of the physical properties of each component is initialized to complete the iterative solution calculation, and the mass transfer flux of the gas phase volatile components in the falling film viscosity increasing reaction process is obtained, and the mass transfer coefficients of water and ethylene glycol are substituted.

[0074] It is necessary to process the polymer flow behavior on the internal components of the falling film viscosity increasing reactor. The polymer flow is set to be a low-speed laminar motion under an extremely low Reynolds number. The liquid film thickness is much smaller than the axial scale of the falling film tube. On the basis of the full development of the liquid film flow, the flow development process of the liquid film with the variable viscosity fluid can be effectively observed and analyzed.

[0075] See also Figure 1 The internal components of the polyester viscosity-enhancing falling film viscosity-enhancing reactor of the present invention are vertical, smooth and vertical pipes. The melt forms a liquid film under the action of gravity and flows circumferentially along the smooth outer wall. The liquid film forms a three-dimensional symmetrical flow pattern in the central axis of the falling film tube. As the reaction proceeds, the devolatilization efficiency increases, and the polymer viscosity gradually increases. As the liquid film flow of the variable viscosity fluid develops, the axial velocity distribution of the polymer is uneven when it flows outside the tube. The present invention uses MATLAB software to establish the free falling liquid film flow process outside the tube of the falling film viscosity-enhancing reactor.

[0076] (IV) Construction of falling film viscosity reactor model

[0077] The main process is to substitute the reaction kinetics model, gas-liquid two-phase mass transfer model and fluid dynamics model into the material balance equation to construct a group of partial differential equations. The input value in the falling film viscosity increasing reactor is the initial condition. The final first-order partial derivative of the change of each component is 0, which is the boundary condition. The number of partial differential equations, time steps and spatial discrete points are set. The material balance equation is discretized by the finite difference method, and the discretized ordinary differential equation is solved by ODE15 function programming in MATALB.

[0078] Reference Figure 2 This is the MATLAB workflow diagram. Importing the above modules into the material balance equation can proceed to the falling film reaction unit module solution stage. It needs to be set up item by item in MATLAB. The specific steps are as follows:

[0079] (1) The initial setting of the reactor length, flow rate, diffusion coefficient, number of spatial discrete points, spatial step, time span and units in the calculation domain are consistent with Aspen Plus units; the basic function solving method is set, and the present invention adopts ODE15s to solve the equation.

[0080] (2) Setting operating conditions: In the present invention, the operating pressure is 100 Pa, the temperature is 560 K, and the initial flow rate is set in consideration of the melt viscosity.

[0081] (3) The model is set up. In order to more realistically predict the falling film viscosity increasing process, the present invention selects a combination of reaction kinetics analysis, gas-liquid two-phase mass transfer analysis and high viscosity fluid dynamics behavior analysis to describe the changes of polymers in the falling film viscosity increasing reactor.

[0082] (4) The present invention solves the material balance equation by calling the function files of each module in the .m script file. (V) Construction of the whole process of falling film viscosity increasing reaction

[0083] The automatic control interface (ActiveX) of Aspen Plus was called to import the output data of its process as the model input value, and MATLAB was run to calculate the material balance equation to obtain the changes of polyester molecular weight, terminal carboxyl group, terminal hydroxyl group, diethylene glycol content, characteristic viscosity and other variables with the reaction progress.

[0084] See also Figure 3 The present invention uses a typical polyester five-reactor process flow as a reference. The first esterification reactor, the second esterification reactor and the first precondensation reactor adopt a full mixed flow model, and the second precondensation reactor and the final polycondensation reactor adopt a plug flow model. The present invention uses Aspen Plus to construct a polyester five-reactor process model.

[0085] (VI) Analysis of simulation results of falling film viscosity enhancement process / Analysis of operating conditions of falling film viscosity enhancement process

[0086] Reference Figure 4 This is the workflow diagram for the interaction between MATLAB and Aspen Plus. The operation results of Aspen Plus are imported into MATLAB software for processing and calculation. This method also effectively improves the flexibility of process design. The interactive method is to call the automatic control interface (Active X) of Aspen Plus and import it into MATLAB. The node path of the component ethylene glycol in the outflow stream is Aspen.Application.Tree.FindNode('\Data\Streams\HP-L\Output\MOLEFLOW\MIXED\EG').

[0087] Figure 5 This is the axial distribution diagram of molecular weight (MWN) in the polyester falling film reaction. The molecular weight at the reactor inlet is 21290 g / mol. According to the data of the simulation results of the present invention, it can be concluded that the molecular weight of the reactor outlet material is 39681 g / mol, and its molecular weight gradually increases in the axial direction.

[0088] Figure 6 It is the axial distribution diagram of the terminal carboxyl group ([T-COOH]) and the terminal hydroxyl group ([T-OH]) in the polyester falling film viscosity increasing reactor. According to the data of the simulation results of the present invention, it can be concluded that as the reaction proceeds, the contents of the terminal carboxyl group and the terminal hydroxyl group gradually decrease along the axial direction, and the terminal carboxyl group content of the reactor outlet material is 18 mmol / kg, and the terminal hydroxyl group content is 32 mmol / kg.

[0089] Figure 7 : This is the axial distribution diagram of the mass fraction of diethylene glycol (DEG) and terminal diethylene glycol groups ([T-DEG]) in the polyester falling film viscosity increasing reactor. According to the data of the simulation results of the present invention, it can be concluded that as the reaction proceeds, the formation of by-product diethylene glycol and terminal diethylene glycol groups is suppressed.

[0090] Figure 8 The axial distribution diagram of molecular weight (MWN) in the falling film viscosity increasing reactor at different temperatures. According to the data of the simulation results of the present invention, it can be concluded that as the temperature gradually increases, the polymer molecular weight increases linearly in the axial direction, and the temperature reaches 563K. Due to the intensification of thermal cracking reaction, the molecular weight growth rate is negatively correlated with temperature. It is better to maintain the overall temperature of the falling film viscosity increasing reactor between 553-563K.

[0091] Fig. 9 and Fig.10The axial distribution diagrams of terminal carboxyl groups ([T-COOH]) and terminal vinyl groups ([T-VIN]) in membrane viscosity-enhancing reactors at different temperatures are shown. According to the data of the simulation results of the present invention, it can be concluded that after the temperature reaches 563K, the terminal carboxyl groups and terminal vinyl groups gradually increase in the axial direction, which will cause the downstream polymer products to turn yellow and be easily hydrolyzed.

[0092] Fig.11 The axial distribution diagram of molecular weight (MWN) in the falling film viscosity increasing reactor at different pressures. According to the data of the simulation results of the present invention, it can be concluded that with the increase of the vacuum degree, the molecular weight gradually increases. After the pressure reaches 0.1 kPa, the molecular weight growth rate slows down. It is better to maintain the overall pressure of the falling film viscosity increasing reactor at about 0.1 kPa.

[0093] Fig.12 ] is an axial distribution diagram of terminal carboxyl groups ([T-COOH]) in a falling film viscosity increasing reactor at different pressures. According to the data of the simulation results of the present invention, it can be concluded that the higher the vacuum degree, the lower the terminal carboxyl group content in the falling film viscosity increasing reactor.

[0094] In summary, the present invention aims to obtain the regularity analysis of the continuous polymerization-falling film viscosity increasing reaction process by the process simulation method, and clearly show the influence of temperature and pressure in the reactor on the component distribution. Provide good guidance for the industrial operation of the falling film viscosity increasing process. The present invention proposes a simulation method for the distribution of performance indicators of components outside the melt tube in the falling film viscosity increasing reactor and a process operation condition analysis method suitable for the falling film viscosity increasing process, which provides a feasible idea for expensive experimental tests and industrial improvements, promotes the design and development of liquid phase viscosity increasing melt direct spinning process, and provides a comprehensive and reliable modeling method for the development of high viscosity melt polycondensation reactors in the liquid phase viscosity increasing process. To this end, the present invention adopts a polyester falling film viscosity increasing reaction process simulation method, and establishes a falling film viscosity increasing reaction process model based on the interactive method of MATLAB and Aspen Plus, which fully considers the physical and chemical changes inside the reaction. The simulation method consists of six parts: polymerization reaction kinetic model analysis, gas-liquid two-phase mass transfer analysis, falling film fluid dynamics behavior analysis, falling film viscosity increasing reactor model construction, falling film viscosity increasing reaction full process construction, falling film viscosity increasing process simulation result analysis / falling film viscosity increasing process operation condition analysis. The invention is mainly used for designing and manufacturing a falling film viscosity increasing reactor in liquid phase viscosity increasing and improving the operation of industrial production process in liquid phase viscosity increasing.

Claims

1. A method for simulating and analyzing the polyester falling film viscosity increasing reaction process, characterized in that include: Conduct polymerization reaction kinetic model analysis, gas-liquid two-phase mass transfer analysis, and falling film fluid dynamics analysis on polyester; The reaction kinetics model, gas-liquid two-phase mass transfer model and fluid dynamics model were used to perform material balance on the entire polyester falling film viscosity increasing reaction process, boundary conditions and initial conditions were set, and the material balance equation was solved by numerical calculation to establish the polyester falling film viscosity increasing reactor model. The entire process of polyester melt falling film viscosity increasing reaction is constructed according to the polyester reaction production process. The index parameters of polyester melt with a certain degree of polymerization obtained by polycondensation are used as input values, and the partial differential equations of the reaction rate are calculated. The performance parameters of the polymerization product and the content information of each characteristic component are output, and the simulation results of the polyester falling film viscosity increasing reaction process are analyzed.

2. The method according to claim 1, characterized in that: The polymerization reaction kinetic model includes a chain growth reaction process that generates by-products of water and hydroxyl compounds; The polymerization reaction kinetics model analysis comprises the following steps: (1) Determine the main reaction and side reactions in the polymerization process: Use the "chain segment analysis" method to simplify the reaction into a limited number of basic chain segment units, with the condensation chain growth reaction as the dominant reaction, and determine the reaction equations for the generation of aldehydes, hydroxyl compounds, hydroxyl condensates, water, and terminal olefins; (2) Determination of reaction rate constant and equilibrium constant: Describe the effect of temperature on the reaction rate constant using the Arrhenius equation, specify the pre-exponential factor and activation energy in the equation, determine the reversible reaction equilibrium constant, and solve for the forward and reverse reaction rate values; (3) Establishing reaction kinetic equations: Use the reaction kinetic model to analyze the reaction kinetic equations of each component, and compile and import the established equation group into an executable function script file in the numerical calculation software.

3. The method according to claim 1, characterized in that: The gas-liquid two-phase mass transfer analysis comprises the following steps: (1) According to the component targets to be analyzed in the gas-liquid two-phase, select an appropriate physical property model and set relevant property values, including one or more of relative molecular mass, critical temperature, pressure, compressibility, gas-liquid phase pressure, molar volume, polymer molecular weight and viscosity characteristic parameters, and store the properties in a global data array; (2) A simulation analysis method for the devolatilization process of small molecules in high-viscosity polymer melts. According to the gas-liquid phase equilibrium process, the volatile components in the system are determined, the gas-liquid equilibrium equation at the interface is constructed by calling the attribute groups of each component, and the corresponding settings are made in the numerical calculation software; The volatile components are specifically: according to the significant influence of each volatile component on the reaction process, the volatile components in the gas phase mainly include hydroxyl compounds and water, and the liquid phase includes hydroxyl compounds, water, condensates of hydroxyl compounds and aldehydes, and the phase equilibrium process parameters are set for the volatile components in the gas and liquid phases; (3) Determine the reactor equipment structure and process condition parameters of the falling film viscosity increasing reaction process that affect the gas-liquid mass transfer rate, introduce the mass transfer coefficient to calculate the mass transfer flux of the gas phase components, and iteratively calculate the mass transfer coefficient based on the gas phase mass transfer flux during the operation of the reactor in industry; (4) Initialize the output attribute group of each component to complete the iterative solution calculation and obtain the mass transfer flux of the gas phase volatile component in the polyester falling film viscosity increasing reaction process.

4. The method according to claim 1, characterized in that: The falling film fluid dynamics behavior analysis includes the following steps: determining the molecular diffusion coefficient in the flow process according to the low-speed laminar polymer motion, establishing the convection-diffusion equation, and setting relevant model parameters in the numerical calculation software, including material flow rate, dynamic viscosity and flow velocity of micro-element in the free falling liquid film area.

5. The method according to claim 1, characterized in that: The construction of the polyester falling film viscosity increasing reactor model comprises the following steps: (1) Based on the polymerization reaction kinetics, gas-liquid mass transfer kinetics and falling film fluid dynamics, the volume microelement mass balance equation along the axial flow direction of the fluid in the falling film viscosity increasing reactor was established; (2) Boundary conditions were set according to the operating parameters of the falling film viscosity increasing reactor in industry, the discrete format was selected, and the material balance equation was solved using the numerical integration method; (3) Define and initialize variables, constants, and parameters, use the software solver to solve the material balance equation, and output key process performance indicators for the gas and liquid phases.

6. The method according to claim 5, characterized in that: (3) The variables, constants and parameters include one or more of the number of components, the number of points discrete in a spatial direction, the number of ordinary differential equations to be solved, and the flow rate of the molten polymer; The key process performance indicators of the gas-liquid phase include one or more of number average molecular weight, intrinsic viscosity and terminal carboxyl content.

7. The method according to claim 1, characterized in that: The construction of the polyester melt falling film viscosity increasing reaction process includes the following steps: (1) calling the automatic control interface of the process simulation software to import the discharge data output from the previous reaction process of the falling film viscosity increasing reactor as the model input value, running the numerical calculation software to calculate the material balance equation, and obtaining the change of variables with the reaction progress; (2) Create a component object model object for process simulation, open and run the model file, set the user interface visibility, and run it in the numerical calculation software to obtain the output information of each component.

8. The method according to claim 7, characterized in that: In (1), the variables include one or more of the molecular weight of the polymer product, the concentration of terminal carboxyl groups, the concentration of terminal hydroxyl groups, the content of hydroxyl condensates, and the intrinsic viscosity.

9. The method according to claim 1, characterized in that: The analysis of the simulation results of the falling film viscosity increasing reaction of polyester also includes the process simulation calculation of different falling film viscosity increasing reactor operating conditions, and the analysis of the influence of operating conditions on the falling film viscosity increasing reaction effect, including: Import the process simulation file into the numerical calculation software for processing, output and display the acquired data as one or more of data tables, graphs or curves, observe and analyze the simulation calculation results, and understand the distribution of performance indicators of each axial component in the falling film viscosity increasing process; In the numerical calculation software, the falling film viscosity increasing reactor unit module is iteratively calculated, and the influence of different operating parameters on the reaction effect is systematically adjusted and analyzed. Through multiple simulation runs, key operation data are collected and compared and analyzed.

10. The method according to claim 9, characterized in that: The different operating parameters include one or more of temperature and pressure; The key data include one or more of reaction product concentration, polymer molecular weight and viscosity change.

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